Vulcanization of rubber



i at ent eci fiec. 19 1939 2 1 VULCANIZATION OF RUBBER Joy G. Lichty, Stow, Ohio, assignor to Wingfoot Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Application June 30, 1936,

Serial No. 88,209

17 Claims. (Cl. 260-788) This invention relates to the process of treataromatic thiazyl me c p e e e Salts ing rubber and, more particularly, to the proviof l-mer'capto 3-methyl benzothiazole, 1-mer-' sion of improvements in accelerating the vulcanaD -phenyl bcnzothiazole, l-mercapto 3- ization of rubber. It also includes the products dimethyl benzothiazole. 1-mereapt0 5-I1it10 h 5 of the process, zothiazole, l-mercapto 5-chlor benzothiazole, 5

It has heretofore been known to vulcanize rubl-merealpm 4I1it10 henZOthiaZOle. her in the presence of the mercaptothiazoles and D O y y beIlZOthiaZOle. e p ei also in the presence of metallic salts of the mer- -methoXy ben p Y captothiazoles, such as the zinc and lead salts beIIZOthiaZOIe, t Lmereepto naphthelthiazeles.

10 of mercaptobenzothiazole, and other mercapto aromatic thiazoles of the 10 By this invention it has been discovered that benzene and naphthalene series. the ammonia and organic amine addition prod- Of the Organic amines Which y b employed nets of zinc salts of mercapto aromatic thiazoles in the P ac e Of the invention, the P y and are in general more powerful accelerators than secondary sa d amines in Particular, the zinc mercapto aromatic thiazoles themselves. the saturated p y amines are p e e AS 15 Also, the addition products of the invention are a e pr v the m n h uld for he mos usually more soluble in petroleum hydrocarbons satisfactory results be more stable than dimethyl and in rubber than the zinc aromatic thiazyl amine, or, in other words, should be less volatile mercaptides. This property makes the addition at room temperatures than dimethyl amine. products of the invention particularly valuable Illustrative of such p y and Secondary 30 in latex compounds. urated amines are diethyl amine, di-n-propyl The addition products of the invention may be amine, di isopropyl amine, ethyl isopropyl amine, prepared by merely bringing the organic amine, ethyl n-butyl amine, di isobutyl amine, methyl or ammonia, and the zinc salt of the mercapto amyl amine, cyclohexyl amine, N-methyl cyclogo'aromatic thiazole together, preferably in a liqhexyl amine, N-ethyl cyclohexyl amine, hexauid dispersion, and generally in suspension or sohydro beta phenethyl amine, hexahydro benzyl lution in water. The reaction appears to be simamine, decahydro alpha or beta naphthyl amine. -ply one-of addition and is generally exothermic. hexahydro 0- or p-toluidine, hexahydro 0- or In certain cases, it is advisable to heat the rep-phenetidine, hexahydro 0- or p-anisidine, action mixture to be sure that the materials have N-methyl hexahydro 0- or p-phenetidine, n-butyl 30 reacted completely. Where the amine employed amine, the amyl primary amines, n-heptyl amine, is a liquid, it is possible to use no extraneous piperidine, pyrollidine, morpholine, tetrahydro liquid dispersing agent. Also, the zinc salt. may alpha furfuryl amine, ethylene diamine, n-probe dissolved or suspended in other dispersing pylene diamine, sym. clibutyl ethylene diamine, agents, such as alcohol, benzene, xylene and gasosym. dimethyl ethylene diamine, N-methyl tetra- 35 line. The amine or ammonia and the zinc arohydro alpha furfuryl amine, N-ethyl tetrahydro matic thiazyl mercaptide usually react in molecalpha furfuryl amine and isobutyl amine.

ular proportions but in many cases two or three Other amines which may be employed in the or perhaps more mols of the amine or ammonia practice of the invention are beta and alpha will add to one mol of the zinc mercaptide. furfuryl amine, the phenalkyl primary amines 40 The preferred compounds of the invention are such as benzyl amine and beta phenethyl amine, those which are stable at normal room temperaand the N-alkyl phenalkyl secondary amines such tures. In general, such compounds are those in as N-methyl benzyl amine, N-ethyl benzyl amine which the additory amine portion is an amine and N-methyl beta phenethyl amine. It will be which is relatively non-volatile. Thus, the amine observed that all of these amines with the ex- 45 addition compounds which are more stable than ception of the alicyclic amines contain a CH2- the dimethyl amine complex are preferred in the group attached to the amino nitrogen atom and, practice of the invention, although dimethyl al"o, at least one hydrogen attached to said amiamineand the less stable aliphatic amineand no nitrogen atom. In general, however, the folammoniaderivatives are also included within the lowing class of amines is satisfactory: alicyclic, 50v

scope of the invention. phenalkyl, furfuryl and tetrahydro furfuryl pri- Of the zinc aromatic thiazole mercaptides, zinc mary amines, aliphatic primary amines having benzothiazyl mercaptide is most preferred in the not more than ten carbon atoms, N -a1kyl alicyclic practice of the invention although it will be unsecondary. amines in which the alkyl group has derstood that the class of zinc aromatic thiazyl not more than five carbon atoms, dialkyl alkylene 55 mercaptides of the benzene and naphthalene sediamines in which the alkyl and alkylene groups ries is also preferred. Illustrative of other zinc have not more than five carbon atoms each,

N-alkyl phenalkyl secondary amines in which the alkyl group has not more tahan five carbon atoms, dialkyl amines having not more than eight carbon atoms, N-alkyl tetrahydro furfuryl secondary amines in which the alkyl group has not more than five carbon atoms, and poly methylene secondary amines in which the poly methylene chain may be interrupted by an oxygen atom.

Example 1 Further illustrative of the invention is the preparation of the addition product of ethylene diamine and zinc benzothiazyl mercaptide which was prepared by heating to the boiling point a mixture of 39.7 grams of zinc benzothiazyl mercaptide, 33 grams of 60% aqueous ethylene diamine and 200 cc. of water. Only a part of the zinc salt went into solution, the remainder of the reaction product remaining as an oil. The aqueous layer was then decanted from the oil. On cooling, 10.2 grams of a solid (A) melting at 178-179" C. separated from the aqueous layer. The oily layer solidified on cooling, giving 35.7 grams of a somewhat impure product melting at a lower temperature. It is believed to consist principally of solid (A) and a small amount of impurities. Solid (A) was in pure form and is believed to be the addition product of 3 mols of ethylene diamine with one mol of zinc benzothiazyl mercaptide. An analysis of the product melting at 178-179 C. gave an average nitrogen content of 18.92%, an average sulphur content of 21.95% and an average zinc content of 11.38% as compared with the theoretical nitrogen, sulphur and zinc contents of the addition product of zinc benzothiazyl mercaptide and 3 mols of ethylene diamine of 19.4%, 22.2% and 11.3%, respectively.

Example 2 In another illustrative example a suspension of 0.1 mol of zinc benzothiazyl mercaptide and 0.22 mol of cyclohexylamine in 200 cc. of water was heated to boiling. A yellow solid which was quite insoluble in water was obtained on cooling in the amount of 51.5 grams. It melted with decomposition over the range of from 73 to C. and is believed to be the addition product of 1 mol of zinc benzothiazyl mercaptide and two mols of cyclohexyl amine.

Example 3 The addition product of ammonia and zinc benzothiazyl mercaptide was prepared by passing an excess of ammonia into 59.6 grams of finely divided zinc benzothiazyl mercaptide. After permitting the product to stand overnight it was found to weigh 62.4 grams. By analysis, this product was found to be the addition product of 1 mol of ammonia and 1 mol of zinc benzothiazyl sulphide.

Per cent N found 9.64, 9.58 Per cent N calc. for C14I-IsN2S4Zn.NH3 10.1

Example 4 Upon the addition of 28.7 grams of mixed' amyl primary amines to 39.7 grams of zinc benzothiazyl mercaptide an exothermic reaction took place. The mixture was heated for a few minutes on a hot plate to assure a complete reaction. A small amount of solid, which was found to be zinc oxide present as an impurity with the zinc benzothiazyl mercaptide, did not go into solution. The liquid reaction product was then extracted several times with water in order to remove the excess amine and was then dissolved in benzene and the zinc oxide thereafter filtered off. The solvent was removed from the filtrate by heating to 50 C. at a pressure of 50-60 mm. A yield of 58.6 grams was obtained. The theoretical yield for a product containing 2 mols cf the primary amyl amines and one of the zinc mercaptide is 57.1 grams. Upon analysis, an average nitrogen content of 8.95% and an average zinc content of 11.15% were found. This compared favorably with the theoretical nitrogen and zinc contents of the addition prodnot of 2 mols of primary amyl amines with 1 mol of zinc benzothiazyl mercaptide of 9.8% and 11.4%, respectively.

Example 5 A mixture of 39.7 grams of zinc benzothiazyl mercaptide and 33.3 grams of tetrahydro alpha furfuryl amine was warmed slightly on a hot plate, causing all materials to go into solution. The product was cooled, washed with water, and dissolved in benzene. llhe solution was then filtered to remove impurities, dried and the solvent removed by heating to a temperature of 70 C. at 60 mm. pressure. The product is believed to be the addition product of 2 mols of the amine and one mol of the zinc mercaptide with approximately 10% present.

Example 6 19.9 grams of zinc benzothiazyl mercaptide (0.05 mol) were suspended in 200 cc. of petroleum ether. 5.1 grams of piperidine (0.06 mol) were added thereto and the mixture stirred for a period of one hour at room temperature. The product after being filtered, washed with water and dried, was obtained in an amount of 24.0 grams and was a light yellow solid melting at -200 C. It is believed to be the addition product of one mol of piperidine and one mol of the zinc mercaptide.

Example 7 4.4 grams of n-butyl amine dissolved in 50 cc. of petroleum ether were added to a suspension of 20 grams of zinc benzothiazyl mercaptide in 150 cc. of petroleum ether. The mixture was permitted to stand for a period of 30 minutes with occasional stirring. After filtering, washing with water and drying, the product was obtained as a tan sticky semi-solid in the amount of 22 grams. Nitrogen analyses indicated that it was the addition product of one mol of n-butyl amine and one mol of zinc benzothiazyl mercaptide.

Other illustrative compounds of the invention may be prepared similarly. Exemplary are the zinc benzothiazyl mercaptide addition products of dipropyl amine, hexahydro oor p-toluidine, N-methyl cyclohexyl amine, N-methyl tetrahydro alpha furfuryl amine, N -ethyl tetrahydro alpha furfuryl amine, N-methyl hexahydro ophenetidine, pipecoline, sym. dibutyl ethylene diamine, methyl amyl amine, dibutyl amine, N ethyl cyclohexyl amine, benzyl amine, diethyl amine, and of the high boiling alkylene poly amines (obtained in the preparation of ethylene diamine, principally diethylene triamine and triethylene tetramine). Others are the addition products of zinc benzothiazyl mercaptide and of zinc 3-methyl benzothiazyl mercaptide with beta phenethyl amine, N-methyl benzyl amine, isobutyl amine, heptyl amine, ethanol amine, methyl propyl amine, methyl isobutyl amine, sym. dimethyl ethylene diamine, and morpholine. Other zinc aromatic thiazyl mercaptides of the of the solvent still benzene and naphthalene series may be used instead of the zinc benzothiazyl mercaptide and the zinc 3-rnethyl benzothiazyl mercaptide of the examples.

In general, the compounds of the invention, while valuable for use in latex compounding, may also be used in most of the usual rubber formulae.

Generally they 'are more powerful acceleratorsthan the zinc aryl thiazyl mercaptide from which they are prepared. Illustrative of one rubber stock in which the compounds of the invention have been found suitable is the following:

Parts by weight ESmoked sheet rubber 100 Zinc oxide Sulphur 3 Accelerator 0.5

.tained. The results are as follows:

Max. elong. kgsJcm.

in percent Cure in ruins. at F.

PRODUCT OF EXAMPLE 1 ZINC BENZOTHIAZYL MERCAPTIDE No cure. No cure.

at temperatures of'240C.with goodultimate tensiles.

While the preferred embodiments of the invention have been described in detail herein, it will be understood that the invention is not so limited but that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. Thus, while the molecular proportions have been given in most instances, these figures are not known definitely in all cases to be the true or only proportions inwhich the amines and the zinc aryl thiazyl mercaptides may be com-- bined in the final products, although these are believed to be correct. ,Also, the melting points or decomposition points, as they maybe called, of many of the compounds have in general a fairly wide range. This is probably for the reason that after some of the heating, portions of the amine and zinc mercaptide starting materials, resulting from dissociation, are present with the addition product. The melting points described were conducted in the normal atmosphere (open capillary tube).

It is intend-ed that the patent shall cover, by suitable expression in the appended claimsfall features of patentable novelty inherent in the v invention.

This application is a continuation-in-part of application Serial No. 85,546, filed June 16, 1936, now Patent No. 2,129,621.

What I claim is:

1. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of zinc benzothiazyl mercaptide and an organic amine containing at least one hydrogen atom attached to the amino nitrogen atom, and vulcanizing.

2. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of zinc benzothiazyl mercaptide and a saturated organic amine containing at least one hydrogen atom attached to the amino nitrogenatom, and vulcanizing.

3. The processof accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of zinc benzothiazyl mercaptide and a saturated primary amine, and vulcanizing.

4. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of zinc benzothiazyl mercaptide and cyclohexyl amine, and vulcanizing.

5. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of zinc benzothiazyl mercaptide and piperidine, and vulcanizmg.

6. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of zinc benzothiazyl mercaptide and amyl amine, and vulcanizing.

7. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of a zinc benzothiazyl mercaptide and a primary amine, and vulcanizing. 8. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of a zinc benzothiazyl mercaptide and an organic amine containing at least one hydrogen atom attached to the amino nitrogen atom, and vulcanizing.

9. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of a zinc aromatic thiazyl mercaptide and a saturated amine containing at least one hydrogen atom attached tothe amino nitrogen atom, and vulcanizing.

10. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of a zinc aromatic thiazyl mercaptide of the benzene and naphthalene series and an amine compound s lected from the group consisting of ammonia, alicyclic, phenalkyl, furiuryl and tetrahydro furfuryl primary amines, aliphatic primary amines having not more than ten carbon atoms, N-alkyl alicyclic secondary amines in which the alkyl group has not more than five carbon atoms, dialkyl alkylene diamines in which the alkyl and alkylene groups have not more than five carbon atoms each, N-alkyl phenalkyl secondary amines in which the alkyl group has not more than five carbon atoms, dialkyl amines having not more than eight carbon atoms, N-alkyl tetrahydro furfuryl secondary amines in which the alkyl group has not more than five carbon atoms, poly methylene secondary amines and oxy poly methylene secondary amines, and vulcanizing.

11. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of a zinc benzothiazyl mercaptide and a primary aliphatic amine, and vulcanizing.

12. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of a zinc benzothiazyl mercaptide and a saturated secondary amine, and vulcanizing.

13. The process of accelerating the vulcanization of rubber which comprises incorporating in a rubber mix the addition product of a zinc benzothiazyl mercaptide and an amine containing at least one CH2 group attached to the amino,- nitrogen atom and at least one hydrogen atom attached to said amino nitrogen atom, and vulcanizing.

14. The vulcanizates obtainable according to the process of claim 1.

15. The vulcanizates obtainable according to the process of claim 9.

16. The vulcanizates obtainable according to the process of claim 3.

17. The vulcanizates obtainable according to the process of claim 4.

JOY G. LICHTY. 

